Compressor capacity control



Jan. 28,

FIG. I

FIG. 2

W. J. WEST ETAL COMPRESSOR CAPACITY CONTROL 2 Sheets-Sheet 1 3e josaulsqfi I L 1 44 K/ \X/ -34 3 x Z: 7 3| 42 54777 L 39 48 2 6 I6 47 42- u A 21 /1 '3 INVENTOR.

WEST JOHN W. SEIGART ATTORNEY.

WALTER J.

Jan. 28, 1964 w w s ETAL 3,119,550

COMPRESSOR CAPACITY CONTROL Filed Feb. 9, 1961 2 Sheets-Sheet 2 FIG. 3

1 N VEN TORS.

WALTER J. WE JOHN W. SEIG ATTORNEY.

3,119,550 COMPRESSOR CAPACETY CONTROL i alter 1?. West, Syracuse, and John W. Seigart, North Syracuse, N.Y., assignors to Carrier Corporation, Syracuse, N.Y., a corporation of Delaware Filed Feb. 9, 1961, Ser. No. 88,091 13 Claims. (Cl. 230-4) This invention relates to a fluid compressor and more particularly to a refrigerant compressor having improved mechanism for controlling the capacity of such compressor and for reducing the cycling of the compressor during load fluctuations. Further, the invention relates to improved cylinder bypass control mechanism.

In a fluid compressor designed to operate at relatively constant speed, the load on the system in which the comperssor is arranged may sometimes vary resulting in inefficient operation of the compressor unless the capacity of the compressor can be varied to comply with the system variations.

One of the methods for varying the capacity of a reciprocating compressor operating at constant speed is to provide some means of by-passing some or all of the cylinder entrapped vapor back to the suction side of the compressor from some point in the cylinder or the discharge manifold. On multi-cylinder compressors a variable capacity has been achieved by bypassing the full discharge of certain of the cylinders back to the suction side of the compressor. In a four cylinder compressor, one pair of cylinders may be manifolded together and arranged to deliver to the discharge side of the compressor at all times. The other pair of cylinders is manifolded to gether and arranged to discharge to the suction side of the compressor or to the discharge side of the compressor according to the load. Suitable controls responsive to the load imposed on the compressor are normally employed. Thus, a capacity reduction of fifty percent is possible with a four cylinder compressor when one pair of cylinders is unloaded. Similarly in a six cylinder compressor which operates with three cylinders in pairs, the discharge of only one pair of cylinders may be directed to the suction side of the compressor to effectuate a onethird reduction in capacity or two pairs of cylinders may be directed to the suction side of the compressor to effectuate a two-thirds reduction in capacity. In some applications it has been found that present capacity control arrangements generally do not provide 100 percent capacity when the compressor is fully loaded, as is desired. Further, there was a desire to replace the three-way solenoid valves often used in the present bypass capacity control arrangements with simpler, less expensive two-way solenoid valves.

An object of the present invention is to provide a refrigerant compressor having an improved capacity control in which the disadvantages or deficiencies of prior constructions is obviated.

Another object of the present invention is to provide a compact, improved cylinder bypass type capacity control arrangement for unloading one or more cylinders of a refrigerant compressor.

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cation with the discharge manifold, a first path placing the second cylinder in fluid flow communication with the discharge manifold, a second path of fiuid flow between the discharge port of the second cylinder and the suction port of the second cylinder, means for opening and closing the second path, a third path of fluid flow between the discharge manifold and the suction port of the second cylinder, fluid in at least a portion of the third path serving to exert pressure upon the opening and closing means when flow through the third path is restricted, means in the third path to close the third path in response to load conditions imposed on the compressor thus increasing the pressure of fluid in the third path to close the second path, and control means to actuate the means in the third path to open the third path, thus actuating the opening and closing means to open the second path.

The attached drawing illustrates a preferred embodiment of my invention, in which FIGURE 1 is a view partly in section and partly in elevation of a portion of a compressor including the apparatus of the present invention, the components being shown in the loaded condition;

FIGURE 2 is a view partly in section and partly in elevation of a portion of the compressor including the apparatus of the present invention, the components of the capacity control being shown in the unloaded position, and

FIGURE 3 is a cross-sectional view of a multi-cylinder compressor including apparatus of the present invention.

Referring to FIGURE 3 of the drawing there is disclosed a compressor 10, the compressor including the capacity control of the present invention. The compressor 10 includes a pair of cylinders 9, 11 manifolded together by discharge manifold 23. Cylinder heads 8, 12 are secured to the compressor 16 above each of the open cylinders 9, 1 1 respectively by bolts 13 to close the top of the cylinders. Pistons 7, 14 are movab ly disposed within each of the cylinders 9, 11 respectively. It will be understood that any number of cylinders may be employed as desired with a piston in each cylinder and that each pair of cylinders may be manifolded together. In one embodiment of the invention, two pairs of cylinders are placed in communication with a third pair of cylinders which is connected to the discharge line of a conventional refrigerating system. Referring to FIGURE 1 of the drawing, valve plate 15 is placed between the cylinder head 12 and the compressor 10. Cylinder head gasket 16 and valve plate gasket 17 are disposed on opposite sides of valve plate 15 to prevent the escape of perssure from Within the compressor. The cylinder communicates with the cylinder head through the discharge A further object of the present invention is to provide a cylinder bypass type capacity control arrangement having a discharge side bleed arrangement to effectuate full design capacity when the compressor is fully loaded.

A still further object of this invention is to provide an apparatus for capacity control of a fluid compressor that is compact and more reliable than present controls. Other objects of the invention will be readily perceived from the following description.

This invention relates to a reciprocating compressor comprising a first cylinder, a second cylinder, a discharge manifold, the first and second cylinders being in communiport 18 and suction port 19in the valve plate 15.

Afiixed to the valve plate are a discharge valve 20 and a suction valve 21. On the suction stroke of the piston, gases are drawn into the cylinder through the suction port 19 and chamber 32 from the suction manifold 22. On the discharge stroke the compressed gas is forced into the discharge chamber 29 through the discharge port 18. The cylinder discharge pressure will force open the discharge piston check valve 24 to permit the passage of the refrigerant gas into the discharge manifold 23. Check valve 24 is biased to the closed position by spring 26 disposed between valve 24- and support 25.

Within the cylinder head is a partition means 27 which divides the head into a discharge chamber 29 and a suction chamber 30. The chambers 29 and 30 can be con- 3 is placed in communication with suction manifold 22 by an internal passage in the compressor.

A piston 34 is adapted to close the opening 33 in response to discharge pressure in a manner to be set forth below. The piston is biased by spring 35 to the open position. Spring 35 is mounted on spring guide 36 which is connected to the solenoid valve assembly 38. One end of spring 35 abuts retaining ring 37 and the other end engages retaining lip 36' of guide 36. The body 39 of the solenoid valve assembly is secured to the cylinder head 12 by suitable bolts 40. Solenoid valve assembly gasket 41 is provided between the cylinder head 12 and the body 39 to prevent the leakage of gases from the compressor.

Means are provided for placing the discharge manifold in communication with the suction manifold. Such means comprise a passage 42 in the valve plate, a passage 43 in the body 39 which communicates with the valve stem chamber 44, a gas bypass port 45 in the body 3? and a passage 59 in the cylinder head. A bleed orifice or restriction 46 is provided in passage 43 in the body. Strainer 47 may be placed in the passage 43 to remove particles of dirt that may be in the gas.

The gas bypass port 45 may be opened and closed by valve 48 actuated by the solenoid 49. The valve is biased closed by gravity or by a spring (not shown). The solenoid or power means may be energized by a thermo stat or pressurestat in response to temperature or pressure as the requirements of the particular application may be.

Operation Considering the operation of the apparatus, on the suction stroke of the piston the gas enters the cylinder 11 from the suction manifold 22, through chamber 32, through the suction port 19 and past suction valve 21. On the discharge stroke of the piston the cylinder suction valve 21 is closed and the gas is forced through discharge port 18 and by discharge valve 28 into the discharge chamber 29. From the chamber 29, the gas flows by the check valve 24 into the discharge manifold 23. Discharge manifold 23 is in communication with each of the other cylinders of the compressor. Inasmuch as the other cylinder 9 is loaded at all times, when solenoid 49 is deenergized, bypass port 45 is closed by valve 48 and pressure builds up in the discharge manifold and in the passages in body 39 to overcome spring 35 and move piston 34 to the right as viewed in FIGURE 1 to close opening 33. The cylinder 11 will continue to operate fully loaded until the solenoid valve control is energized and the gas bypass port is opened.

When the solenoid valve 49 is energized, the solenoid valve 48 will move to open the gas bypass port 45. Refrigerant gas will be bled to the suction manifold through the open gas bypass port and the passage 50 in the cylinder head. A reduction in pressure behind the valve piston 34 will take place because the rate of bleed through the gas bypass port is greater than the rate of supply through the bleed orifice 46. When the pressure behind the piston has been reduced sufliciently, the valve spring 35 will force the valve piston 34 back, opening the gas bypass from the discharge manifold to the suction manifold. Discharge pressure in the discharge manifold (from the working cylinder 9) will close the discharge piston check valve isolating the compressor discharge manifold from the individual unloaded cylinder manifolds. The cylinder will continue to operate fully unloaded until the solenoid valve device is deenergized and the gas bypass port 45 is closed.

In a typical compressor application employing the present invention, the cylinders of a six-cylinder compressor are divided into three pairs, each pair having a common cylinder head. One of the pairs has no control arrangement and is, therefore, never unloaded. Thus pressure is always available in the discharge manifold 23 to operate the piston 34 to close opening 33 when the solenoid is deenergized and valve stem 48 closes oil the passage through body 39. A capacity control arrangement may be provided on one of the three pairs of cylinders to effectuate approximately 33 /3 percent capacity control, or on two of the three pairs of cylinders to effectuate approximately either 33 /3 percent or 66% percent capacity control. The present bypass type capacity control arrangement will efiectuate full design capacity when the compressor is fully loaded as distinguished from similar prior arrangements which provided less than percent capacity when fully loaded.

The present invention provides a simplified, compact capacity control system. The capacity control mechanism including a discharge side bleed arrangement and solenoid actuated control means is efiicient and reliable in operation.

While we have described a preferred embodiment of our invention it will be understood our invention is not limited thereto, since it may be otherwise embodied in the scope of the following claims.

We claim:

1. In combination with a reciprocating compressor having a cylinder including a movable piston therein, a suction manifold, a valve plate having a suction port and a discharge port therein and a suction valve and a discharge valve for controlling flow through said port, a cylinder head for the compressor cylinder, such cylinder head including a partition separating a discharge chamber and a suction chamber, such chambers communicating respectively with the discharge port and the suction port, said partition having an opening placing said chambers in communication, and a discharge manifold communicating with the discharge chamber in the cylinder head, unloader means comprising a piston for closing said partition opening in response to discharge pressure, means biasing said piston to open said partition opening, means defining a bleed passage communicating said discharge manifold and said suction chamber, said bleed passage having a restriction therein, and means for controlling flow through said bleed passage in response to load conditions imposed in the compressor, whereby when said bleed passage is open, said piston is actuated to open said partition opening and discharge gases circulate from said discharge chamber to said suction chamber to said suction manifold and when said bleed passage is closed, said piston is actuated to close said opening and discharge gases flow through the discharge chamber to said discharge manifold.

2. A reciprocating compressor as in claim 1 wherein said piston biasing means comprises a spring.

3. In combination with a reciprocating compressor having a cylinder including a movable piston therein, a suction manifold, a cylinder head, a discharge manifold, means for controlling the unloading of said cylinder comprising means defining a passage communicating the dis charge manifold and the suction manifold, said passage having a restriction therein, a partition in said cylinder head having an opening therein for communicating the discharge manifold and the suction manifold, solenoid actuated valve means for opening and closing said passage in response to a load condition, and means for closing said partition opening in response to closing of said passage whereby when the passage is closed the partition opening is closed and the cylinder is loaded and when the passage is open the partition opening is open and the cylinder is unloaded.

4. In a compressor the combination of means defining a cylinder, a piston movable within said cylinder, a cylinder head, valve means between said cylinder and said cylinder head, said valve means including a discharge valve and a suction valve, a partition in said cylinder head defining a first chamber and a second chamber therein, a discharge manifold in communication with the first chamber of said cylinder head and adapted to communicate with a pressure source, a suction manifold in communication with the second chamber of said cylinder head, means defining an opening in said partition, piston means for opening and closing said partition opening, means biasing said piston means to the open posi tion, means defining a passage for placing said discharge manifold and said suction manifold in communication, and power-actuated means for opening and closing said passage, said passage communicating with said piston means whereby when said power-actuated means closes the passage, the piston means is actuated to close the partition opening and prevent bypass of gas between the first chamber and the suction manifold and when said poweractuated means opens the passage, the piston means is biased to open the partition opening and bypass the gas between the first chamber and the suction manifold.

5. A compressor as in claim 4 wherein said piston actuated means comprises valve mechanism and a solenoid for actuating said valve mechanism.

6. In a reciprocating compressor, the combination of a first cylinder, a second cylinder, a discharge manifold, a suction manifold, said cylinders being in communication with said discharge manifold through discharge ports and being in communication with said suction manifold through suction ports, means for placing the discharge port of the second cylinder in communication with the suction port of the second cylinder, said means including an element adapted to prevent communication between the discharge port of the second cylinder and the suction port of the second cylinder, means for imposing discharge manifold pressure against said element to actuate the element to prevent communication between the discharge port and the suction port of the second cylinder, and means for relieving the imposed discharge manifold pressure to actuate said element to permit communication between the discharge port and the suction port of the second cylinder, thereby unloading the second cylinder.

7. A reciprocating compressor as in claim 6 including means interposed between the second cylinder and the discharge manifold to prevent flow of fluid from the discharge manifold to the second cylinder.

8. A reciprocating compressor as in claim 7 including control means for the relieving means responsive to load conditions imposed on the compressor.

9. In a reciprocating compressor, the combination of a first cylinder, a second cylinder, a discharge manifold, said cylinders being in communication with said manifold, a first path of fluid fiow placing the second cylinder in fluid flow communication with the discharge manifold, a second path of fluid flow between the discharge port of the second cylinder and the suction port of the second cylinder, means for opening and closing the second path,

a third path of fiuid flow between the dis-charge manifold and the suction port of the second cylinder, said third path having orifice means therein, fluid in at least a portion of said third path serving the exert pressure upon said opening and closing means when flow through the third path is restricted, means in said third path to close said third path in response to load conditions imposed on the compressor thus increasing the pressure of fluid in the third path to actuate said opening and closing means to close said second path, and control means to actuate said means in said third path to open the third path, thus actuating said opening and closing means to open the second path.

10. A reciprocating compressor as in claim 9 including means for regulating fluid flow from the discharge manifold to the second cylinder.

11. A reciprocating compressor as in claim 9 including means for regulating fluid flow in the first path.

12. In a reciprocating compressor, the combination of cylinder means having a compression chamber, piston means in said cylinder means, a suction manifold, a suction valve regulating flow of refrigerant between the compression chamber and the suction manifold, a cylinder head above the piston means, a discharge valve regulating the flow from said compression chamber to said head, a discharge manifold, a check valve controlling the gaseous flow from said discharge manifold to said head, means for placing said discharge manifold in communication with said suction manifold, means defining a passage connecting said discharge manifold with said suction manifold, said passage having a restriction therein, means for closing said communicating means in response to discharge pressure, and means for controlling movement of said closing means, said controlling means including means for ciosing said passage to the flow of discharge gas and thereby moving the closing means to close the communicating means.

13. A reciprocating compressor as in claim 12 wherein said closing means comprises a piston.

References Cited in the file of this patent UNITED STATES PATENTS 1,847,229 Swanson et al. Mar. 1, 1932 2,296,304 Wolfert Sept. 22, 1942 2,338,240 Gould Jan. 4, 1944 2,350,537 Scott June 6, 1944 2,639,725 Albright May 26, 1953 2,715,992 Wilson Aug. 23, 1955 2,755,987 Gerteis July 24, 1956 2,961,148 Courtney Nov. 22, 1960 2,991,924 Ramsay July 11, 1961 3,021,790 Brunson Feb. 20, 1962 

1. IN COMBINATION WITH A RECIPROCATING COMPRESSOR HAVING A CYLINDER INCLUDING A MOVABLE PISTON THEREIN, A SUCTION MANIFOLD, A VALVE PLATE HAVING A SUCTION PORT AND A DISCHARGE PORT THEREIN AND A SUCTION VALVE AND A DISCHARGE VALVE FOR CONTROLLING FLOW THROUGH SAID PORT, A CYLINDER HEAD FOR THE COMPRESSOR CYLINDER, SUCH CYLINDER HEAD INCLUDING A PARTITION SEPARATING A DISCHARGE CHAMBER AND A SUCTION CHAMBER, SUCH CHAMBERS COMMUNICATING RESPECTIVELY WITH THE DISCHARGE PORT AND THE SUCTION PORT, SAID PARTITION HAVING AN OPENING PLACING SAID CHAMBERS IN COMMUNICATION, AND A DISCHARGE MANIFOLD COMMUNICATING WITH THE DISCHARGE CHAMBER IN THE CYLINDER HEAD, UNLOADER MEANS COMPRISING A PISTON FOR CLOSING SAID PARTITION OPENING IN RESPONSE TO DISCHARGE PRESSURE, MEANS BIASING SAID PISTON TO OPEN SAID PARTITION OPENING, MEANS DEFINING A BLEED PASSAGE COMMUNICATING SAID DISCHARGE MANIFOLD AND SAID SUCTION CHAMBER, SAID BLEED PASSAGE HAVING A RESTRICTION THEREIN, AND MEANS FOR CONTROLLING FLOW THROUGH SAID BLEED PASSAGE IN RESPONSE TO LOAD CONDITIONS IMPOSED IN THE COMPRESSOR, WHEREBY WHEN SAID BLEED PASSAGE IS OPEN, SAID PISTON IS ACTUATED TO OPEN SAID PARTITION OPENING AND DISCHARGE GASES CIRCULATE FROM SAID DISCHARGE CHAMBER TO SAID SUCTION CHAMBER TO SAID SUCTION MANIFOLD AND WHEN SAID BLEED PASSAGE IS CLOSED, SAID PISTON IS ACTUATED TO CLOSE SAID OPENING AND DISCHARGE GASES FLOW THROUGH THE DISCHARGE CHAMBER TO SAID DISCHARGE MANIFOLD. 